This invention relates to a method of making a building board or the like and to the building board so made.
Conventional inorganic building boards include fibre reinforced cement and gypsum boards, the latter often lined on both sides with kraft paper. These boards are tried and tested building products which are cost effective and which do not support combustion. The ability of these boards to attenuate sound transference by absorption is generally poor as a result of their impervious, dense nature. Additionally, these boards are heavy with bulk densities generally approaching two, requiring that they be supported at close centres during fixing, and resulting in the fact that handling and transportation is costly, that breakage is frequent, and that costs are accordingly affected.
The concept of cellular cement or gypsum boards is not new, but in the former case unless the cement board is autoclaved during production, the setting time is long, requiring protracted periods in the formers, and full strength is developed only after a period of weeks, and the foamed cement is subject to cracking, particularly at densities less than 1000 k/m.sup.3. In the case of gypsum, poor mechanical properties result. In both cases, extension using expanded perlite, vermiculite or mineral wool results in excessive friability.
There is thus a need for a method of making a building board which is light, cost effective, with good acoustic properties, which does not lose its structural integrity on wetting, which has good mechanical properties, and whose density may be varied.